envelope

Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

n. A flat paper container, especially for a letter, usually having a gummed flap.

n. Something that envelops; a wrapping.

n. Biology An enclosing structure or cover, such as a membrane or the outer coat of a virus.

n. The bag containing the gas in a balloon or airship.

n. The set of limitations within which a technological system, especially an aircraft, can perform safely and effectively.

n. The coma of a comet.

n. Mathematics A curve or surface that is tangent to every one of a family of curves or surfaces.

idiom push the envelope To increase the operating capabilities of a technological system.

idiom push the envelope To exceed the existing limits in a certain field; be innovative.

from Wiktionary, Creative Commons Attribution/Share-Alike License

n. A paper or cardboard wrapper used to enclose small, flat items, especially letters, for mailing.

n. Something that envelops; a wrapping

n. A bag containing the lifting gas of a balloon or airship; fabric that encloses the gas-bags of an airship.

n. A mathematical curve, surface, or higher-dimensional object that is the tangent to a given family of lines, curves, surfaces, or higher-dimensional objects.

n. A curve that bounds another curve or set of curves, as the modulation envelope of an amplitude-modulated carrier wave in electronics.

n. The shape of a sound, which may be controlled by a synthesizer or sampler.

n. The information used for routing an email that is transmitted with the email but not part of its contents.

n. An enclosing structure or cover, such as a membrane.

n. The set of limitations within which a technological system can perform safely and effectively.

n. The nebulous covering of the head or nucleus of a comet; a coma.

n. An earthwork in the form of a single parapet or a small rampart, sometimes raised in the ditch and sometimes beyond it.

v. Alternative spelling of envelop.

from the GNU version of the Collaborative International Dictionary of English

n. That which envelops, wraps up, encases, or surrounds; a wrapper; an inclosing cover; esp., the cover or wrapper of a document, as of a letter.

n. The nebulous covering of the head or nucleus of a comet; -- called also coma.

n. A work of earth, in the form of a single parapet or of a small rampart. It is sometimes raised in the ditch and sometimes beyond it.

n. A curve or surface which is tangent to each member of a system of curves or surfaces, the form and position of the members of the system being allowed to vary according to some continuous law. Thus, any curve is the envelope of its tangents.

n. A set of limits for the performance capabilities of some type of machine, originally used to refer to aircraft; -- it is often described graphically as a two-dimensional graph of a function showing the maximum of one performance variable as a function of another. Now it is also used metaphorically to refer to capabilities of any system in general, including human organizations, esp. in the phrase push the envelope. It is used to refer to the maximum performance available at the current state of the technology, and therefore refers to a class of machines in general, not a specific machine.

Mind you - to the naked monkey eye this envelope is absolutely indistinguishable from the envelopes issued by Tor ... but who can fathom why a cat will obsessively hoard one object, and ignore an identical one?